ECN Forum Forums General Topics of the Trade General Discussion Area industrial load calculation

I have been asked to do a load calculation for a 8,000 SQFT industrial building. The building is being used for plating.

Since this is my first industrial load calc, i though i ask you guys who have more experience in industrial that may be able to help me.

Thanks for your time.

Plating is generally a very heavy user of electricity.

Step #1 is to look at their plans, and equipment. If the equipment is fairly modern, and pretty much pre-fab, then you will be able to size your circuits accordingly. Rather than sizing to 125% FLA, though, I would use 140% for the conductor sizing ... because of ambient temperatures.

If the equipment is a hodge-podge of second hand equipment, then allow for double the load of the equipment presented. Trust me, they're going to be adding more stuff ....

You'll have a crane somewhere ... remember that OCPD and grounding rules differ for that stuff.

Almost all of your circuits will be dedicated, and will be sized for the equipment. While I am usually a big fan of placing receptacles everywhere, I would have as few as possible in the plating area. Te reason: corrosion. I will return to this in a bit ....

Lighting: LOTS of light. It is important that the lighting be reasonably white, and free from glare. I can't think of anything better than the T-5 high bay fluorescents. Great care should be taken to place the lights where they are readily accessible (you DON'T want to have to place a ladder over a tank), and where they cannot be struck by a crane pr forklift load. Plastic sleeves, as used in food service, are recommended. Sealed fixtures are not.

Corrosion will be your biggest challenge. Threaded connections, and wire connections, should be coated with noalox- or they will corrode. EMT is probably OK, though immediately next to the tanks PVC has its' advantages. No matter the material, run ground wires.

A final caution as to grounding: Remember that plating is not only a corrosive industry, but one that uses DC, and has the equipment itself as a conductor. Make sure everything is bonded together - pretend it's a swimming pool - and that ground connections are accessible (for inspection and maintenance).

Thank you Reno for the detailed reply. The building, panels, conduits, wiring... are all existing. Nothing is being added or removed yet. The city has requested this load calculation done according to 2002 NEC, in order to see if the service, conduits, panels, circuitry the whole nine yards are up to nec 2002 standards.

So i guess what i am asking for is, how do you do an industrial three phase load calculation with an existing load?

Thanks for your time.

If it is existing, then all you really need to do is measure amp draw with everything on. Only id this amount is more than 80% of the main service size do you need to look at it closer.

As for individual circuits, look at the FLA of the equipment it's feeding, multiply by 125%. The circuit ought to be that big, or larger.

For the sub-panels, treat them like the main service: measure at full load, see if it's large enough.

Thank you very much for your help and the info.

If the are asking for a load calculation this is what they are probably looking for:

1) General Illumination, 220-16 (b) @ 125%
2) General Purpose Receptacles, 220-44, Table 220-44, and 220-14 (a) which ever is greater. First 10KVA @ 100%, the remainder @ 50%.
3) Water Heaters 422-13 @ 125%
4) Out Side Lighting 210-19 (a)(1) @ 125%
5) Heat 220-51 Non-coincidental Loads 220-60 @ 100%
6) Motor Loads 220-50 (List every single motor out) @ 100%
7) Sign Circuit 600-5a, and 220-14 (f) @125%
8) 25% of the Largest Motor Load, Sec. 460-24 & 220-18 (a)

That is it, sharpen your pencil, get your notebook out and walk the plant and collect all that data, and list it out in excel.

Thank you for the info and your time.